Photographic materials containing carbodhmides



United States Patent O \a Delaware lfl'o Drawing. Filed July 24, 1958,Ser. No. 750,590

17 Claims. (Cl. 96-111) This invention relates to photography, andparticularly, to photographic gelatin layers and light-sensitivephotographic gelatin emulsion layers containing the quaternary ammoniumsalts of an N,N'-d=isubstituted carbodiimide as a hardening agent.

Gelatins used in the production of photographic materials have beenreacted with a variety of hardening and modifying agents such as alum,chrome alum; formaldehyde, glyoxal :or other aldehydes; keto-alcohols,nitroaldehydes, nitroureas, and the like to improve the physicalcharacteristics of the gelatins. In all cases, however, the reagentsreact with the gelatin to yield a derivatized gelatin containing thereagent or a part thereof as an integral part of the gelatin structureWith the result that some questionable improvement in physicalproperties is accompanied by an impairment of photographic properties.

It is an object of our invention to prepare hardened photographicgelatin layers, having improved physical and photographiccharacteristics.

Other objects will be apparent from the following description.

We have found that compositions of matter adapted to form hardenedgelatin layers including gelatin silver halide emulsion layers can beprepared by using the products resulting from the addition to an aqueousgelatin solution of a small portion of a quaternary ammonium salt of anN,N-disubstituted carbodiimide. These layers have new and improvedproperties, display unique characteristics and differ from unreactedgelatin and silver halide emulsion layers by their melting points andphotographic characteristics.

The water or alcohol soluble quaternary ammonium salts of theN,N'-d-isubstituted carbodiimdes used in accordance with this inventionare characterized by the following general formulae:

wherein A represents an organic radical such as an aliphatic radical,e.g., methyl, ethyl, propyl, isopropyl, nbutyl, isobutyl, tert.-butyl,allyl, crotyl, B-hydroxyethyl, methoxy-methyl-B-bromoallyl, and thelike; an aromatic radical, e.g., phenyl, tolyl, Xylyl, naphthyl,chlorophenyl, bromophenyl, iodophenyl and the like; and alicyclicradical, e.g., cyclohexyl, bornyl, menthyl and the like; and aheterocyclic radical, e.g., pyridyl, quinolyl and the and ice

like; R and R are lower alkyl radicals, e.g., methyl, ethyl, propyl,isopropyl, butyl and the like; B and B which may be alike or differentrepresent alkylene, arylene or aralkylene radicals, e.g., propylene,phenylene, tolylene, propylphenylene and the like; X is an anion, e.g.,chloride, bromide, iodide, methosulfate, ethosulfate,p-toluenesulfonate; and n is a positive integer not greater than 2.

The disubstituted carbodiimides are prepared by treating anN,N-disubstituted symmetrical or unsymmetrical thiourea, having at leastone tertiary amino group, with a desulfurizing agent, particularly theoxide of a heavy metal such as lead or mercury, as described inBerichte, vol. 71, pages 1512-21; vol. 73, pages 467-477, 1114 1123;vol. 74, pages 12851296 and vol. 75, pages 100-5; Annalen, vol. 560,pages 222-231; also Journal of Organic Chemistry, vol. 21, pages 1024-6.

The N,N'-disubstituted carbodiimides with the tertiary amino group areconverted into the quaternary ammonium salt by reacting them directly,or in the presence of a solvent-diluent such as ethyl acetate,chloroform, benzene, or toluene, or mixtures thereof, with a suitablequaternizing agent such as methyl bromide, ethyl bromide, methyl iodide,ethyl iodide, dimethyl sulfate, diethyl sulfate, methyl p-toluenesulfonate, ethyl p-toluene sulfonate and the like. Molar equivalents ofthe quaternizing agent or a slight excess thereof are employed if onlyone of the tertiary nitrogen atoms is to be quaternized while di-molarequivalents are used when two tertiary amino groups are to be convertedinto the quaternary forms. i

The following is a suggestive listing of N,N-disubstituted carbodiimideswhich may be employed for the purpose herein set forth: N-is opropyl-N'-4-dimethylaminophenyl) carbodiimide ethyl p-toluenesulfonateN-phenyl-N-(4-dimethylaminophenyl)carbodiimide ethyl p-toluenesulfonateN,N-di(4-dimethylaminophenyl) carbodiimide rnonoethobromideN,N-di(4-dimethylaminophenyl) carbodiimide monoethiodideN,N'-di(4-dimethylarninophenyl)carbodiimide dimethiodideN,N-di(4-diethylaminophenyl)carbodiimide methyl ptoluenesulfonateN,N'-di(4-dipnopylaminotolyl)carbodiimide ethyl p-,

toluenesulfonate N,Nt-di(4-dimethylaminophenyl)carbodiimide mono- 'tionproducts.

N-isopropyl-N'- ('y-dimethylaminopropyl) carbodiimide ethobromid eN-methoxymethyl-N- (v-d imethylaminopropyl) carbodiimide ethylp-toluenesulfonate N,N'-di-('y-pyridyl)carbodiimide monomethosulfateN,N-dl- ('y-pyridyl carbodiimide di'ethosulfate The reaction between thegelatin (bone, hide, pigskin or degraded, etc.) and the carbodiimide'canbe carried out by dissolving or swelling the gelatin in water and thenadding the quaternary ammonium salt of the carbodiimide in anyconvenient inert solvent media, preferably water, alcohol, or mixturesthereof.

The gelatin'concentration may vary over a wide range, e.g., from 0.5 to20 percent by weight. The amount of carbodiimide quaternary ammoniumsalt employed in the reaction may range from gms. to 50 gms. per kg. ofdry gelatin although amounts ranging from to 25 gms. of carbodiimide perkg.'of dry gelatin are preferred. The reaction temperature may be variedfrom 5 C. to 75 0, preferably from to 50 C., but care must be taken toavoid prolonged heating at such higher temperatures at which the gelatinbecomes unstable. The

pH may be varied through the mildly acid or mildly alkaline rangealthough a pH between 5 and 8 has been found most suitable in aqueoussystems.

The gelatin solutions and photographic emulsions which have beenhardened with the carbodiimide quaternary salts yield products whichhave valuable properties. They yieldphotographic films which have highermelting points and which are less affected by storage and processing atelevated temperatures. The viscosity of the gelatin solution containingthe carbodiimide is not increased on holding prior to coating, so thatno compensation must be made to correct for constantly increasingviscosities'prior to and during the coating operation. Most important isseveral. It will be observed that this reaction differs entirely fromthe type of modification of gelatin obtained by the use of conventionalhardeners such as formaldehyde, keto-alcohols, etc., because the latterenter the gelatin molecule or form the cross-links which bind thegelatin molecules.

The materials obtained by our procedure can be further modified by theuse of external acids such as acetic,.

butyric, stearic, or other aliphatic acids; by benzoic, toluic, or othervariously substituted aromatic acids; or by alicyclic or heterocycliccarboxylic acids. These acids are caused to react with the amino groupsof gelatin by the use of carbodiimides as condensing agents. Thereaction is analogous to those which occur when carbodiimldes are mixedwith gelatin alone, and the reaction products are assumed to have thefollowing general formula:

Gel-NH-COR Gel-O ON wherein R and R are hydrogen or hydrocarbon radicalthe feature that emulsions hardened with our quaternary salts do notcause the undesirable effects known as after hardening but reacha'stabilized melting point within a few days of storage at roomtemperature.

Our procedure offers special advantages when applied to gelatins whichcontain substantial amounts of degrada- Such materials frequently havedesirable photographic properties, but cannot be used commercially inview of their poor physical properties. Such gelatins can besubstantially improved with our process through relinking of thedegradation products to the parent gelatin molecules. More particularly,gelatin samples which conand constitutes the residue of the amine usedin the reaction.

Our invention includes in one of its preferred forms the use ofcarbodiimide quaternary ammonium salts in conjunction with conventionalgelatin hardeners such as formaldehyde, glyoxal, glycol aldehydes,diketones, halogen-substituted aldehyde acids such as mucochloric acidand mucobromic acid, formylacrylic acid, glyoxylic acid,halogen-substituted ketones such as chloroacetone,

'; dichloroacetone or dibromoacetone, hydroxy-substituted ketones suchas dihydroxyacetone, amino aldehydes, nitro aldehydes, nitro alcoholsand the like. In this case, the effects induced by the use of thecarbodiimide quaternary ammonium salts and the effects produced by thehardeners supplement each other and are of a synergistic nature.

7 Thus, different properties may be obtained, or considertainsubstantial amounts of degradation products are characterized bydepreciated properties, such as lowered melting points and settingpoints, decreased rigidity moduli (meaning the resistance of gelatingels to deformation) increased Bloom value (measuring the resistance ofthe surface to penetration) as described in the Encyclopedia of ChemicalTechnology, vol. VII, page 151 (1951) increased brittleness andincreased watersolubility. These deficiencies are ameliorated by thetreatment with carbodiimides.

The reaction between the gelatin is believed to be attained in such-away that the carbodiimide may serve solely as a condensing orcross-linking agent as illustrated by the following hypothetical generalequation in which'the symbol gel represents the residue of a gelatinmolecule for reasons of simplicity:

carbodiimide quaternay HaN-Gel-C 0213 HzN-Gel-O O OH 7 ammonium saltSince gelatin contains both free amine and free carboxyl groups, thistype of reaction may be either an intraor intermolecular condensation.Only gelatin molecules are involved in cross-linking. Obviously, thisreaction need not stop with two gelatin molecules but can involve andthe carbodiimide ably lower amounts of hardening agents may be employedto achieve the desired physical properties. The reaction withformaldehyde in the presence of carbodiimide quaternary ammonium saltsis believed to proceed as follows:

- HzN-Gel-OONH-Gel-COOH lumen-coon H0110 0% I HzN-GQON-Gel-GOOH Theamounts of aldehyde or other organic hardener used in this combinationhardening will yary between 1 and 8 grams of aldehyde per kilogram ofgelatin depending on the aldehyde chosen and the degree of hardeningdesired. In any event the amount of organic hardener used in combinationhardening Will not exceed 50 percent of that amount needed to producethe selected degree of hardening when the organic hardener is used byitself.

While the above reactions have been illustrated with respect to thecarboxy and amino groups of the gelatin molecules, it should be kept inmind that these molecules contain additional functional groups such asguanidino, aliphatic or aromatic hydroXyl, mercapto or disulfidelinkages which may enter new bondings in the reaction. It is, therefore,evident that the aforementioned illustrations are of an explanatorynature only andshould not be construed as limiting the invention tothese mechanisms.

The following examples will serve to illustrate the previously describedinvention, although it is to be understood that the invention is not tobe limited thereto.

Melting Melting Mg. f carbodilmide salt per g. of gel. point, 0. point,10

days, C.

The photographic properties of the material which contained 30milligrams of carbodii-mide salt per gram of gelatin which did not meltat 90 C. were compared with the photographic properties of an unhardenedemulsion and of a formaldehyde hardened emulsion. The following resultswere obtained:

Fog Speed Contrast High speed negative Fresh Aged Fresh Aged Fresh AgedUnhardened 0. 19 0.26 110 03 1. 5 1. 4 Formaldehyde. 0. 17 0. 24 9379 1. 5 1. 4 Oarbodiimide 0. 12 0. 25 135 123 1. 5 1. 4

It will be noted that the use of carbodiimide hardener increased thespeed of this film by about twenty percent. The speed advantage wasretained in the aged film. Other photographic properties were notaffected. The film hardened with formaldehyde showed a speed loss ofabout 20 percent.

EXAMPLE II Example I was repeated with the exception that a 2 percentsolution of N-cyclohexyl-N-(4-dimethylaminophenyl)carbodiimide ethylp-toluenesulfoniate was used in place of theN,N-di(4-diethylaminophenyl)carbodiimide methyl p-toluenesulfonate. Thefollowing results were obtained:

Melting Melting Mg. earbodiimide/g. gel. point, 0. point,

ays,

The photographic results obtained were similar to those reported inExample 1. Contrast and fog were essentially unchanged while the speedwas noticeably increased. An emulsion hardened with formaldehyde showedloss of speed, contrast and increased fog.

EXAMPLE III A high speed X-ray emulsion containing 8 percent gelatin wasmixed with increasing amounts of a 2 percent aqueous solution ofN-(tert.-butyl)-N'-(' -dimethylaminopropyl)carbodiimi-de ethylp-toluenesulfonate and then coated on filmbase. fter coating, thesamples were 6 stored over saturated K solution for three days. Thefollowing results were obtained:

Melting Melting Mg. earbodiimide/g. gel. point, 0. point, 3

days, C.

The photographic properties of the emulsion. containing 30 mg. ofcarbodiimide per gram of gelatin were compared with an unhardened typeand a film hardened with formaldehyde. The following results wereobtained:

Table I Fog Speed Contrast High speed negative Fresh Aged Fresh AgedFresh Aged Unhardened type 0.10 0.16 107 110 1.7 1.4 Formaldehydehardened- 0.11 0.17 102 85 1.6 0.6 Carbodiirnide hardened 0.12 O. 17 1201.7 1.4

The significantly improved aging behavior of the cardodiimide hardenedfilms with respect to speed and contrast is evident.

EXAMPLE IV Coatings were made as in Example I using both N,N'- di(4diethylaminophenyl)carbodiirnide dimethosulfate and formaldehyde invarious amounts. The following melting points were observed:

Mg. ear- Mg. torm- Melting Melting bodiirnide/ aldehyde] point, 0.point, 10

g. gel. g. gel. days, C.

0 None 34. 7 35.1 10 None 40.1 41. 5 None 1 37. 5 38. 9 None 3 37. 9 39.3 None 6 41. 3 52. 7 10 1 39. 5 45. 7 10 3 40. 5 62. 2 10 6 50. 2 90+ Itwill he noted from this table that the synergistic effect resulting fromthe combined use of formaldehyde and carbodiimide in raising the meltingpoint of the coating is very pronounced.

EXAMPLE V Example IV was repeated with the exception that N-cyclohexyl-N-(4-dimethylaminophenyl) carbodiimide ethylp-toluenesulfonarte was used in place of N,N-di(4-diethylaminophenyl)carbodiirnide dimethosulfate. The following results were obtained:

Mg. ear- Mg. glyoxal/ Melting bodiimlde/ g. gel. point, G.

g. gel.

0 None 34. 9

10 None 36. 2

20 None 39. 5

30 None 40. 7

None 1 36. 4

None 2 39. 3

None 4 41. 9

Thus, a level of carbodiimide which was insufiicient by itself toappreciably harden the emulsion coating, was eifec-tive as a hardenerwhen combined with a glyoxal which by itself was also incapable toappreciably harden the emulsion coatings. The photographic properties of7 the film hardened with the combination of formaldehyde andcarbodiimide were excellent. Even after extended storage, no loss ofspeed and contrast was observed, a positive indication that theundesirable photographic effects of after hardening were obviated.

.Various modifications of this invention will occur to persons skilledin the art. We, therefore, do not intend to be limited in the patentgranted except as necessitated by the appended claims. For instance, inplace of the formaldehyde and the glyoxal illustrated by the examples,other known hardening agents can be used.

This application is a continuation-impart of our application, Serial No.609,529, filed September 13, 1956, now abandoned.

We claim:

1. A silver halide emulsion adapted to form a hardened layer comprisinga gelatin silver halide photognaphic emulsion containing (a) a memberselected from the group consisting of:

and

R2 \NB-N=C=N-B1N wherein A represents members selected from the groupconsisting of methyl, ethyl, propyl, isopropyl, n-butyl, isobu-tyl,tert.-butyl, allyl, crotyl, be-tahyd-roxyethyl,methoxymethyl-beta-bronioal-lyl, phenyl, tolyl, Xylyl, naphthyl,chlorophenyl, bromophenyl, iodophenyl, cyolohexyl, bornyl, menthyl,pyridyl and quinolyl; R and R represent lower alkyls; B and B representmembers selected from the group consisting of propylene, phenylene,tolylene and propylphenylene, X is an anion selected from the groupconsisting of chloride, bromide, iodide, methosulfate, ethosu-lf ate,p-t-oluene sulfonate and n is a positive integer not greater than 2, and(b) an organic hardener selected from the group consisting offormaldehyde, glyox'al, glycol aldehydes, diketones, mucochloric acid,mucobromic acid, formylacrylic acid, glyoxylic acid, ohloroacetone,dichloroacetone, dibromoacetone, dihydroxyacetone, amino aldehydes,nitro aldehydes and nitro alcohols.

2. A composition of matter comprising a solution of gelatin containing(a) a member selected from the group and selected from the groupconsisting of formaldehyde, glyoxa l, glycol aldehydes, diketones,mucochloric acid,

mucobroniic acid, formylacrylic acid, glyoxylic acid, chloroacetone,dichioroacetone, dibromoacetone, dihydroxy acetone, amino aldehydes,nitro aldehydes, and nitro alcohols.

3. A gelatin silver halide light emulsion as defined by claim 1 whereinthe hardening agent of (b) is glyoxal.

4. A gelatin silver halide light emulsion as defined by claim 1 whereinthe hardening agent of (b) is formaldehyde.

5. A composition of matter according to claim 2 wherein the hardeningagent of (b) is formaldehyde.

6. A method of producing a hardened gelatin silver halide emulsion layerin the photographic element which comprises uniformly mixing with anaqueous gelatin silver halide emulsion a hardening amount of (a) amember selected from the group consisting of:

R2 and R2 I: NB-N=o:NBiN

wherein -A represents members selected from the group consisting ofmethyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, tert.-butyl, allyl,crotyl, beta-hydroxyethyl, methoxymethyl-zbeta-bromo-allyl, phenyl,tolyl, Xylyl, naphthyl, chlorophenyl, bromophenyl, iodophenyl,cyclohexyl, bornyl, menthyl, pyridyl and quinolyl; R and R representlower alkyls; B and B represent members selected from the groupconsisting of propylene, phenylene, tolylene and propylphenylene, Xis'an anion selected from the group consisting of chloride, bromide,iodide, methosulfate, ethosulfate, p-toluene sulfonate and n is apositive integer not greater than 2, and (b) an organic hardenerselected from the group consisting of formaldehyde, glyoxal, glycolaldehydes, diketones, mucochloric acid, mucobromic acid, formylacrylicacid, glyoxylic acid, chloroacetone, dichloroacetone, dibromoacctone,dihydroxy acetone, amino aldehydes, nitro aldehydes and nitro alcoholsand coating said emulsion on a support and drying the layer just formed.

7. A method according to claim 6 wherein the hardener of (=b) isformaldehyde.

8. A method according to claim 6 wherein the hardener of (b) is glyoxal.

9. A silver-halide emulsion as defined by claim 1, wherein saidquaternary ammonium salt is N,N'-di(4- diethylaminophenyl)carbodiimidemethyl p-toluenesuldonate.

10. A silver-halide emulsion as defined by claim 1, wherein saidquaternary ammonium salt is N-cy-clohexyl- N'-(4-dimethylaminophenyl)carhodiimide ethyl p-toluenesulfonate.

11. A silver-halide emulsion as defined by claim 1, wherein saidquaternary ammonium salt is N-(tert.butyl)- N ('y di-methylaminopropyl)carbodiimide ethyl p-toluenesulfonate.

12. A composition of matter as defined by claim 1, wherein saidquaternary ammonium salt is N,N-di(4- diethylaminophenyl)carhodiimidemethyl p-toluenesultonate.

13. A composition of matter as defined by claim 1, wherein saidquaternary ammonium salt is N-cyclohexyl-N'-(4-dimethylaminophenyl)carbodiimide ethyl p-toluenesulfonate.

14. A composition of matter as defined by claim 1, wherein saidquaternary ammonium salt is N-(tert.- butyl) N ('ydimethylaminopropyl)carbodiimide ethyl p-toluenesulfonate.

15. A method of producing hardened silver-halide emulsion layers asdefined by claim 6, wherein said quaternary ammonium salt isN,N'-di(4-diethylaminophenyl)carhodiimide methyl p-toluenesulfonate.

16. A method of producing hardened silver-halide emulsion layers asdefined by claim 6, wherein said 5 quuaternary ammonium salt isN-(tert.-buty1)-N'-(' dimethylaminopropyl)carbodiimide ethylp-toluenesulfonate.

1 ii) 1 Referenees Cited in the file of this patent UNITED STATESPATENTS 2,288,226 Carroll et a1 June 30, 1942 2,726,162 Allen et a1.Dec. 6, 1955 2,938,892 Sheehan May 31, 1960 UNITED STATES PATENT OFFICECERTIFICATE OF CORRECTION Patent No. 3,100,704 August 13, 1963 Robert F.Coles et 31.

It is hereby certified that error appears in the above numbered patentrequiring correction and that the said Letters Patent should read ascorrected below.

Column 6, line 20, strike out "High speed negative"; column 8, lines 15to 18, the formula should appear as shown below instead of as in thepatent:

same column 8 lines 59, 63 and 6'7, for the claim reference numeral "1,each occurrence, read 2 column 9, line 6, for "quuaternary" readuaternary Signed and sealed this 30th day of June 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J BRENNER Attesting Officer Commissioner ofPatents

1. A SILVER HALIDE EMULSION ADAPTED TO FORM A HARDENED LAYER COMPRISINGA GELATIN SILVER HALIDE PHOTOGRAPHIC EMULSION CONTAINING (A) A MEMBERSELECTED FROM THE GROUP CONSISTING OF: